Copper-Catalyzed Heteroannulation Route to Indolines

Significance

This work was spurred by the authors’ previous studies into the synthesis of cyclic amidines from 1,n-alkynylamines (S. Chang et al. J. Am. Chem. Soc. 2006, 128, 12366). In the present study, a new synthesis of 2-sulfonylimino­indolines from aromatic 2-alkynylanilines, catalyzed by CuI, is reported. Pd, Ru and other Cu salts were also tested; CuI provided the best yields but only when 2,6-lutidine was used as a base. The substrate scope was adequately studied. For R² = acyl and sulfonyl, only 1,2,3-triazole products were obtained in good yields. The conversion of the iminoindolines into isatin derivatives and oxindoles was also demonstrated.